Diglossia, or the use of two forms of a language in a single speech community, is widespread. Differences between the nonstandard form, used for everyday conversations, and the standard form, used for formal occasions and writing, often extend to phonology as well as grammar and vocabulary. Most preschoolers from diglossic families are routinely exposed to the colloquial nonstandard form during conversations at home because the social setting determines the form their parents use. If early spellings are speech based, exposure to nonstandard phonology should influence the kinds of errors diglossic children make. We investigated this prediction in Rumi Malay that, unlike English, has unambiguous phonology–orthography mappings. For Study 1, two spelling tests (51 words, 26 nonwords) were dictated with standard Malay pronunciation. For words, but not nonwords, the diglossic Singaporean children (N = 52, mean age = 6.5 years) made vowel errors that are consistent with the nonstandard Malay pronunciation they use at home. Study 2 confirmed that these errors are rare for equally proficient Malay spellers from Indonesia who speak standard Malay at home. These results are interpreted as strong evidence for the view that beginners' spellings are based on phonological redintegration of their own speech-based representations.